Internal tree cap and itc running tool

ABSTRACT

Internal tree cap (ITC) adapted to be installed in the bore of a subsea well unit or to an internal tubular element of the same, comprising a locking element for releasably locking the internal tree cap to said subsea well unit or internal tubular element. The ITC further comprises a fluid channel extending through a fluid barrier between the lower and upper part of the internal tree cap, which fluid channel is blocked by a burst element adapted to break and open for fluid flow through the fluid channel when exposed to a predetermined pressure difference over the burst element. The invention also relates to an ITC running tool and a locking mechanism for supporting the ITC in the tool.

The present invention relates to an internal tree cap and a tool forrunning the internal tree cap. In addition, the invention relates tomethods of using the tree cap and the tool.

BACKGROUND

Due to the two-barrier philosophy for subsea hydrocarbon wells, an upperand a lower plug are conventionally installed in the bore of a subseaX-mas tree or its internal elements, such as the tubing hanger. It isknown to replace the upper plug with an internal tree cap, the tree caphaving features in addition to just blocking for fluid connection.

Known internal tree caps are installed and retrieved through a marineriser from a surface installation. Thus, such installing or retrievingoperations are cumbersome since they require the establishment of theriser from the surface and down to the well tree. Establishing the risertakes time and one needs to use a rig. Rigs are not always easilyavailable and are also expensive to rent on a day-to-day basis.

In addition, in some instances the PTV-line (plug testing valve) can beblocked, making it impossible to test the space between the lower plugand the internal tree cap. With a conventional internal tree cap runinside a riser, one faces difficulties solving such problemsaccompanying such situations. For instance, retrieval of the internaltree cap can possibly not be done due to the hydrostatic lock formed bythe sealed-off space below the internal tree cap.

International patent application publication WO2007054644 describes acap for a subsea tree and for use with a tubing hanger. This cap isadapted to be arranged both internally and externally about the treespool, and is not adapted to be landed through a marine riser. It isadapted to be landed on a wire.

Furthermore, patent application publication US20040216885 describes amethod for installing a tree cap on a subsea Xmas tree with the use ofan ROV. The cap has a channel through it in order to provide a vacuum ornegative pressure in the space below the cap, thereby “sucking” the capinto place.

OBJECT

The present invention seeks to solve the above-mentioned problemsrelated to conventional internal tree caps (ITC) and internal tree captools (ICT tool). In addition, the present invention provides for someadvantageous features still not disclosed in the prior art.

THE INVENTION

According to a first aspect of the invention, there is provided aninternal tree cap (ITC) which is adapted to be installed in the bore ofa subsea well unit or to an internal tubular element of the same. TheITC comprises a locking element for releasably locking the ITC to saidsubsea well unit or internal tubular element. The ITC further comprisesa fluid channel extending through a fluid barrier between the lower andupper part of the internal tree cap, which fluid channel is blocked by aburst element which is adapted to break and open for fluid flow throughthe fluid channel when exposed to a predetermined pressure differenceover the burst element. With such an ITC, fluid access to the spacebelow an installed ITC can be provided without the use of an ROV, evenif the PTV line (pressure testing valve) is blocked. This will befurther described below.

Preferably the ITC according to the first aspect of the inventioncomprises a valve arranged in connection with a fluid passage in saidfluid barrier between the upper and lower part of the tree cap. Whenaccess to the ITC is not prevented, for instance by a marine riser, anROV can open the valve in order to provide fluid connection to the spacebelow the ITC.

A pipe can be arranged with fluid connection to the top of said fluidchannel and can advantageously be provided with a bend or a filter inorder to prevent falling debris to block the fluid channel.

The ITC can preferably comprise an outer sleeve reciprocally arranged onan inner sleeve, which outer sleeve is adapted to force a locking splitring outwardly into engagement with a subsea well element or an internaltubular element thereof, when being forced downwards in relation to theinner sleeve. This way, the ITC is adapted to be run by an ITC runningtool, such as the one described further below.

The subsea well unit can be a tree spool and said internal tubularelement can be a tubing hanger arranged in the tree spool.

Preferably, the upper part of the ITC is adapted to be arranged flushwith or lower than the upper part of the subsea well unit, such as atree spool, into which it is arranged.

The ITC can have a hotstab receptacle for an ROV hotstab, with fluidconnection to the space below the internal tree cap, enabling pressuretest of said space by means of an ROV when installed.

According to a second aspect of the present invention, there is provideda method of retrieving an internal tree cap through a marine riser, fromthe bore of a subsea well element, wherein a PTV-line (plug testingvalve-line) is blocked, which blocking has resulted in a sealed offspace between the internal tree cap and a lower barrier, such as a lowerplug. The method comprises the following steps:

a) connecting an internal tree cap retrieving tool to the internal treecap;

b) applying pressure in the riser of such magnitude that a burst elementin a fluid channel between said space and the upper side of the internaltree cap bursts, thereby opening said channel; and

c) pulling up said retrieving tool, thereby disengaging the internaltree cap from engagement with the subsea well unit.

According to a third aspect of the present invention, there is provideda tool for locking an internal tree cap (ITC) to the bore of a subseawell unit or retrieving it from the same, the tool being adapted to lockonto the subsea well unit, directly or indirectly. The tool comprises awire connection member for wire suspension of the tool from a surfaceinstallation and actuation means for locking said internal tree capdirectly or indirectly in the bore of the subsea well unit, and ITCsupport means for supporting the internal tree cap. The tool is adaptedto be retrieved from said subsea well unit and internal tree cap wheninstalled, as said ITC support means is adapted to release the ITC fromthe tool, preferably by actuation with an ROV.

The tool is preferably adapted to move the ITC in a vertical directionto a landed position, and further force an ITC-member verticallydownwards to an ITC locked position. Furthermore, the tool preferablycomprises an indication means for indication of the unlanded, landed andthe locked position, wherein said indication means being visible fromthe exterior of the tool.

In one embodiment the tool can be latched and unlatched to the ITC witha latching handle, and said latching handle can be locked in a latchedposition by means of a locking pin, preventing unintentional unlatchingof the ITC from the tool.

Preferably, the tool is adapted to releasably connect to an outer sleeveof the internal tree cap, and, after landing of the internal tree cap,force said outer sleeve downward by actuating at least one ROV-actuatedhydraulic piston, in order to lock the internal tree cap to a tubinghanger in said bore.

In one embodiment of the tool, the ITC support means comprises a

-   -   a main body with a plurality of locking members arranged along        an outer perimeter of the main body, the locking members being        rotatable supported on the main body about respective rotation        axes;    -   an actuation ring arranged within an inner perimeter of the main        body, said actuation ring comprising a plurality of engagement        elements which extend into engagement slots of the locking        members, so as to rotate the locking members about said axes by        rotation of the actuation ring with respect to the main body;    -   wherein the locking members according to their rotational        position are adapted to assume a locking position, wherein their        perimeter extends a first distance out from the ITC support        means and an unlocked position wherein said distance is shorter        than the first distance, as the distance from the axes of the        locking members to their perimeter varies along the perimeter.

Preferably, the ITC support means can be operated by an ROV through anITC latching handle extending on the exterior of the tool.

According to a fourth aspect of the present invention, there is provideda method for installing an internal tree cap in the bore of a subseawell unit through a marine riser from a surface installation. The methodcomprises the following steps:

a) lowering a running tool down to the subsea well unit through saidriser, the running tool carrying an internal tree cap, until theinternal tree cap has landed in the bore of said subsea well unit;

b) dropping a ball down through said riser, thereby closing a channel insaid running tool;

c) applying pressure in the bore of said riser, thereby providing fordownward movement of a hydraulic piston that forces an outer sleeve ofthe internal tree cap to move downward, which further results in forcinga split ring of the internal tree cap into engagement with the bore orbore profile of the subsea well unit or an internal tubular memberthereof.

Such a method for installation makes it possible to install the ITCaccording to the first aspect of the invention also through a marineriser. Thus, the ITC is not restricted to use with a wire-suspendedrunning tool

According to a fifth aspect of the invention, there is also provided amethod of retrieving an internal tree cap through a marine riser, fromthe bore of a subsea well element, wherein the PTV-line (plug testingvalve-line) is blocked, wherein the blocking has resulted in a sealedoff space between the internal tree cap and a lower plug. The methodcomprises the following steps:

a) connecting an internal tree cap retrieving tool to the internal treecap;

b) applying pressure in the riser of such magnitude that a burst elementin a fluid channel between said space and the upper side of the internaltree cap bursts, thereby opening said channel; and

c) pulling up said retrieving tool, thereby disengaging the internaltree cap from engagement with the subsea well unit.

According to a sixth aspect of the invention, there is provided alocking mechanism for locking to internal or external locking grooves ofa circular bore or member, respectively. The locking mechanism comprises

-   -   a main body with a plurality of locking members arranged along        an inner or outer perimeter of the main body, the locking        members being rotatable supported on the main body about        respective rotation axes;    -   an actuation ring arranged within the inner perimeter of the        main body or outside its outer perimeter, respectively, said        actuation ring comprising a plurality of engagement elements        which extend into engagement slots of the locking members, or        vice versa, so as to rotate the locking members about said axes        by rotation of the actuation ring with respect to the main body;    -   wherein the locking members according to their rotational        position are adapted to assume a locking position, wherein their        perimeter extends a first distance radially out from the locking        mechanism or radially inwardly from the locking mechanism,        respectively, and an unlocked position, wherein said distance is        shorter than the first distance or non-existent, as the distance        from the axes of the locking members to their perimeter varies        along the perimeter.

Such a locking mechanism is suitable for locking a member to theinternal grooves in a bore, such as the internal grooves of a tree spoolor an internal tree cap, such as the one illustrated herein. The lockingmechanism can also be arranged to lock to external grooves of a circularmember, such as externally onto a tree spool. The mechanism is actuatedby rotation of the actuation ring with respect to the main body. Thus,the main body could also be rotated to obtain the same function. It isunderstood that the locking mechanism can lock onto concentric shapes aswell as non-concentric shapes, such as a locking groove with the crosssection of an elliptical circle.

The locking members can have the shape of plates. This will haveadvantage over other solutions as locking pins or expandable splitrings, by being able to adsorb larger forces and by avoiding alteringthe shape (such as a split ring).

The plates can preferably be arranged between two surfaces, of which oneis the surface of the main body. Thus, the plates can preferably besupported with bolts running from one of the surfaces to the other,through said plates.

Instead of arranging engagement slots in the locking members, thelocking members could also be provided with engagement members, such asprotrusions extending into engagement slots in the actuation ring.

As will readily be appreciated by the person skilled in the art, thepresent invention exhibits a plurality of advantages.

The ITC tool gives the possibility of running an ITC without the use ofa marine riser. It is comparably cost-efficient and easy to use.

The ITC can be run both by the tool according to the first aspect of theinvention, and through a marine riser. In addition it exhibitspreferable features giving a plurality of advantages and possibilities.

Having described the main features of the present invention, a moredetailed description of an example embodiment will be given in thefollowing.

EXAMPLE OF EMBODIMENT

In the following, a description of an example embodiment of an internaltree cap (ITC) and an ITC tool according to the invention will be givenwith reference to the drawings, in which

FIGS. 1A and 1B are perspective views of an ITC running tool accordingto the present invention;

FIG. 2 is a top view of the ITC running tool in FIGS. 1A and 1 B;

FIG. 3 is a cross section view of the tool in FIG. 2, along section A-A;

FIG. 4 is a cross section view of the tool in FIG. 2, along section C-C;

FIG. 5 is a cross section view of the tool in FIG. 2, along section D-D;

FIG. 6 is a top view of an internal tree cap (ITC) according to thepresent invention;

FIGS. 7A and 7B are cross section views of the ITC in FIG. 6, along thesurfaces B-B and C-C, respectively;

FIG. 8 is a perspective cross section view of the ITC in FIG. 6;

FIG. 9 is a cross section view of the tool landed on a tree spool,during running of the ITC;

FIG. 10 is a cross section view of an ITC being installed on a tubinghanger with a BPRT (borehole protector running tool) through a marineriser;

FIG. 11 is a cross section view of the ITC in FIG. 10, having beenlocked to the tubing hanger;

FIG. 12 is a cross section view of the top part of an ITC running tool;

FIG. 13 is an enlarged perspective view of the top part shown in FIG.12;

FIG. 14 is a top view of an alternative ITC holding element;

FIG. 15 is a perspective view of parts of the ITC running tool shown inFIG. 12 and FIG. 13;

FIG. 16 is a cross section view of the alternative ITC holding element;

FIG. 17 is a cross section view of an ITC left in the tree spool, withthe running tool retracted; and

FIG. 18 is a cross section view of the ITC in FIG. 17, shown with adebris cap arranged on the tree spool.

In FIGS. 1A and 1B, an internal tree cap running tool 101 according tothe first aspect of the present invention is illustrated. Actually, theITC tool 101 is a rebuilt light tree running tool. The ITC tool 101 isadapted to be suspended on a wire (not shown) over a suspension bracketwith an eye 103 on top of the tool 101. It is thus adapted to be landedon a tree spool (not shown) by means of a winch and an ROV. The tool hasa cylindrical housing part 105 a and a top housing part 105 b. Under thehousing 105 is arranged a funnel 107, ensuring gentle contact betweenthe tool 101 and a tree spool (not shown) when landing the tool 101 ontothe spool. Connected to the top housing 105 b is a circular handling bar109 for protection of the tool 101 and for handling by an ROV (remotelyoperated vehicle) (not shown). Also shown in FIGS. 1A and 1B is an ROVhotstab receptacle 111 for receiving an ROV hotstab. The function ofthis will be explained further below, as will other elements shown inFIGS. 1A and 1B.

FIG. 2 shows the ITC tool from above. Here one can see two ROV hotstabreceptacles 111, the handling bar 109, the top housing 105 b, and thesuspension bracket with the eye 103. The main purpose of FIG. 2 is toindicate the cross sections of the following FIGS. 3, 4 and 5.

FIG. 3 shows a cross section view of the ITC tool 101 through sectionA-A. In this drawing, a latching element 113 is shown supported in thehousing 105 a. The latching element 113 is adapted to move into or outof engagement with an outer groove of the tree spool (see FIG. 9). Toprovide this movement, the latching element 113 is operatively connectedto an actuation ring 115 which can be operated by an ROV (not shown). Inthis manner, the ITC tool 101 can be latched to or unlatched from a treespool. FIG. 9 shows the tool 101 landed on a tree spool.

Also shown in FIG. 3 is an ITC holding element 117. The holding element117 is adapted to hold the ITC by means of a plurality of holding pins119 which are adapted to extend into a mating groove in the outer partof the ITC. In FIG. 3, the holding pins 119 are shown in a non-holdingretracted position. The holding pins 119 are biased towards thisposition by means of springs. When in this position, their inner endsextend into mating grooves 117 c in a rotating inner part 117 a of theITC holding element 117. The said grooves have inclined faces thatdetermine the radial position of the holding pins 119 according theangular position of the rotating inner part 117 a. The rotating innerpart 117 a can be rotated from the outside of the ITC tool 101. This isperformed by rotating an ITC latching handle 121 with an ROV. Thus,after proper installation of the ITC, the ITC can be detached from therunning tool 101.

The process of locking the ITC to the tubing hanger takes place byactivation of two hydraulic pistons 125. Hydraulic pressure can besupplied to their upper hydraulic chamber through one of the hotstabreceptacles 111, by means of an ROV. This pressure will force the ITCholding element 117 downwards, providing a secure connection between theITC and the tubing hanger. This process step will be described furtherbelow (see especially FIG. 9).

FIG. 4 illustrates the section C-C of the tool in FIG. 2, showing mostof the elements shown in the cross section view of FIG. 3. In addition,FIG. 4 shows one of the hotstab receptacles 111, which is attached tothe top housing 105 b. Also shown in FIG. 4 is a tool landing indicatorpin 123. The indicator pin 123 is biased downwards by means of a spring.When the ITC tool 101 is landed on top of a tree spool (FIG. 9), theindicator pin 123 will come into contact with the upper part of the treespool, resulting in an upward movement of the pin 123 with respect tothe rest of the tool 101. When the tool 101 is fully landed on the treespool, the tool landing indicator pin 123 will extend a predeterminedlength above the top housing 105 b. In this manner, the operator willknow when the tool 101 is fully landed, by inspecting the position ofthe pin 123, for instance by means of an ROV camera.

FIG. 5 is an additional view of the ITC tool 101 in FIG. 2, showing thecross section D-D. Here, a extension part 117 b of the rotating innerpart 117 a can be seen extending upwards through the top housing 105 band connected to the ROV-operable ITC latching handle 121.

Having described the main features of an ITC running tool 101 accordingto the first aspect of the present invention, an internal tree cap 201according to the second aspect of the invention will now be described.

FIG. 6 is a top view of an internal tree cap 201 according to the secondaspect of the present invention. In FIG. 6, the cross sections of FIGS.7A and 7B are indicated as B-B and C-C, respectively.

FIG. 7A depicts the cross section B-B of the ITC 201 in FIG. 6. The ITC201 has an outer sleeve 203 which is reciprocally connected to an innersleeve 205. The outer sleeve 203 can slide on the inner sleeve 2005between an upper and lower position. In FIG. 7A (and FIG. 7B) the outersleeve 203 is shown in the upper position. A plurality of shear pins 207extend from the outer sleeve 203 into recesses in the inner sleeve 205,and are inwardly biased by means of springs. When sliding downwards tothe lower position, the shear pins 207 will slide on an inclined face,forcing the pins 207 radially outward, until they snap into aneighbouring lower recess, securing the outer sleeve 203 in the lowerposition. to This position is illustrated in FIG. 8.

The outer sleeve 203 is provided with an inner locking groove 202,adapted to receive holding pins 119 of the running tool 101, orcorresponding locking elements.

Referring to FIGS. 7A and 7B, below the outer sleeve 203 is arranged anITC locking element in the form of a split ring 209. The split ring 209is adapted to expand radially and lock to an inner profile of a tubinghanger (see FIG. 9). In order to expand the split ring 209, the outersleeve 203 is forced downwards, making an inclined face 203 a of theouter sleeve 203 force the split ring 209 radially outwards. Thedownward movement of the outer sleeve 203 is provided by actuating thepistons 125 of the ITC tool 101. This makes the holding element 117force the outer sleeve 203 downwards. When the outer sleeve 203 hasmoved down to its lower position, it is held in place by means of theshear pins 207, as explained above (FIG. 8). For the operator to knowthe position of the pistons 125, a locking indicator 127 (see FIGS. 1Aand 1B) is operatively connected to the ITC holding element 117. Thelocking indicator 127 thus moves vertically along with the pistons 125,indicating the position of the outer sleeve 203 of the ITC 201.

For sealing engagement with the tubing hanger, the ITC 201 is providedwith a pair of seals 225.

In FIG. 9, the ITC 201 is shown connected to the ITC tool 101, whereinthe tool 101 has landed on the tree spool 301 and the ITC 201 has beenlanded and connected to the tubing hanger 303. The outer sleeve 203 ofthe ITC 201 is thus in its lower position, and the split ring 209 isengaged with the inner profile of the tubing hanger 303. After asuccessful pressure test, the ITC tool 101 can be retrieved. The tool101 is disconnected from the ITC 201 as explained above, by turning therotating inner part 117 a, thereby retracting the holding pins 119 fromengagement with the ITC 201.

For retrieving the ITC 201 from the tubing hanger 303 with the ITC tool101, the tool is lowered down onto the ITC 201. In this position, theholding pins 119 are in the retracted position. By rotating the rotatinginner part 117 a of the holding element 117, inclined faces (not shown)of the rotating inner part 117 a will force the holding pins 119 intothe facing grooves of the outer sleeve 203. As the ITC holding element117 now is secured to the outer sleeve 203, actuation of the pistons 125by means of an ROV will force the outer sleeve 203 upwards, and releasethe split ring 209 of the ITC 201 from engagement with the tubing hanger303. The ITC 201 can now be retrieved by unlocking the tool 101 from thetree spool 301 and pulling it up by the wire (not shown). This processis substantially the opposite of installing the ITC 201, as explainedabove.

The ITC 201 according to the second aspect of the present invention canalso be run on a bore protector running tool 401 (BPRT) through a marineriser (not shown), as illustrated in FIGS. 10 and 11. In FIG. 10, theITC 201 has been landed on the tubing hanger 303 inside the tree spool301. Inside the BPRT 401, there is a channel 403 for letting fluid flowfreely in and out of the BPRT bore. The ITC 201 is now to be secured tothe tubing hanger 303 by moving down the outer sleeve 203 to its lowerposition. This is done by moving a hydraulic piston 405 downwards ontothe outer sleeve 203 by applying hydraulic pressure through the marineriser (not shown). To do this, the channel 403 is first closed off bydropping a ball 407 down through the riser and sealingly cover theopening of the channel 403. Pressure in the marine riser is thenapplied, which will provide for pressure in the hydraulic chamber 409above the piston 405. The pressure is transferred through the hydraulicchannels 411.

The resulting movement of the hydraulic piston 405 will move the outersleeve 203 of the ITC 201 downwards, as illustrated in FIG. 11. In thesame manner as explained above, the outer sleeve 203 will force thesplit ring 209 into locking engagement with the tubing hanger 303.

To retrieve the BPRT 401, it must now be disconnected from the ITC 201.This takes place by a further downwardly movement of the hydraulicpiston 405. This movement will result in a retraction of a split ring413 that until this movement was in engagement with an internal grooveof the ITC 201.

To retrieve the ITC 201 with the bore protector running tool 401 (BPRT)through the marine riser, the BPRT 401 lowered against the ITC 201 withthe split ring 413 in extended position. When contacting the upper partof the outer sleeve 203 of the ITC 201, the split ring 413 will beforced radially inward. When moving the BPRT 401 even further down, thesplit ring 413 will snap into the facing groove in the upper part of theouter sleeve 203, thereby constituting a secure engagement with the ITC201. Pulling the BPRT 401 back up will detach the ITC 201 from thetubing hanger, and the ITC 201 can be retrieved through the marine riser(not shown).

Referring again to FIG. 8 (as well as FIGS. 7A and 7B), the ITC 201exhibits a disc valve 211 for opening or closing a fluid passage betweenthe lower and upper part of the ITC 201. The disc valve 211 exhibits alarge handling flange 213 for interfacing with an ROV. Thus, an ROV canopen and close the disc valve 211 from above.

The ITC 201 according to this example embodiment also exhibits a fluidchannel 215 in addition to the disc valve 211, extending between theupper and lower part of the ITC 201. Inside the fluid channel 215 isarranged a burst element in form of a burst disc 217 which is adapted tobreak at a predetermined pressure difference between the upper and lowerpart of the ITC 201. This feature is advantageous if the ITC 201 is tobe retrieved through a marine riser and the PTV-line (plug testingvalve) (not shown) is blocked by debris. The PTV-line is normally usedfor pressure testing between the lower and upper plug, or lower plug andthe ITC. However, if the PTV-line is blocked, and the disc valve 211 isclosed, the ITC 201 cannot be retrieved due to hydrostatic locking ofthe ITC 201. This problem is solved by applying enough pressure in theriser, above the ITC 201, so that the burst disc 217 breaks. Thisprovides venting of the space below the ITC 201, so that it can beretrieved through the riser.

In connection with and above the fluid channel 215 there is a pipe 219with a 180 degree bend, which protects the fluid channel 215 from beingblocked by falling debris.

Referring again to FIG. 7A, the ITC 201 also exhibits an ROV hotstabreceptacle 221. In FIG. 7A, a hot stab dummy 223 is arranged in thereceptacle 221. Through the receptacle 221, an ROV can perform pressuretest of the ITC 201 from below, by applying pressure through thereceptacle 221, into the space below the ITC 201. There is a not shownfluid connection from the receptacle 221 to the space below the ITC 201.Thus, if the PTV-line is blocked by debris, a pressure test can still beperformed by the ROV.

In the following, some examples of further embodiments are given. InFIG. 12 and FIG. 13, the top of an ITC running tool 101′ is shown in aside view and perspective view, respectively. This running tool 101′ isprovided with a cover 105 c′ that covers three hydraulic pistons 125′(not visible), as well as hydraulic lines arranged on top of the tophousing part 105b′. The three hydraulic pistons 125′ have the samefunction as described above (pistons 125), namely to actuate the outersleeve 203′ of an ITC 201′ (not shown) in the vertical direction. Inorder to indicate the vertical position of said outer sleeve 203′ of theITC 201′ when connected to the ITC running tool 101′, an extension part117 b′, corresponding to the extension part 117 b in FIG. 5, extends toa position indication ring 129′. The position indication ring 129′encircles the stem 131′ running from the top housing part 105 b′ to thelifting interface 103′ at the very top of the tool. On the stem 131′ arethree position indications, U, L1, and L2, each representing a specificvertical position of the outer sleeve 203′ of the ITC 201′. The positionU indicates an unlocked position, in which the ITC 201′. The position L1indicates a landed position, wherein the inner sleeve 205′ of the ITC201′ has landed on the tubing hanger 303′ (cf. FIG. 9). The position L2indicates that the outer sleeve 203′ has been forced downwards withrespect to the inner sleeve 205′, in which case the ITC has been lockedto the tubing hanger 303′.

In the manner as described above with reference to FIG. 3, the tool 101′can be latched and unlatched from the ITC 201′ by rotational operationof a latching handle 121′. In order to avoid unintended rotation of thelatching handle 121′, the extension part 117 b′ is provided with anROV-operable locking pin 133′ that extends into a bore 135′ in the stem131′. In this embodiment, the stem 131′ is provided with two such bores135′, enabling the rotational fixation of the latching handle 121′ inthe unlocked position U and the locked position L2, as described above,when the tool 101′ is locked to the ITC 201′.

FIG. 14 shows a top view of an embodiment of an ITC running tool 101″with an alternative ITC support means or ITC holding element 117″ forlatching a running tool 201″ to the ITC. The ITC holding element 117″comprises a main body 118″ non-rotationally arranged within acylindrical housing part corresponding to the part 105 a shown in FIG.5. Connected to an extension part 117 b″ (FIG. 15) is a rotating innerpart 117 a″. The rotating inner part 117 a″ has four guide bolts 117 d″extending into the slots 117 e″ of four holding plates 119″. The holdingplates 119″ are rotationally arranged to the main body 118″ of the ITCholding element 117″, attached with rotation bolts 117 f″. Thus, whenrotating the rotating inner part 117 a″, the holding plates 119″ arerotated since the guide bolts 117 d″ extend into said slots 117 e″. InFIG. 14, the holding plates 119″ are shown in a latched position,wherein a part of them extend outside the circular perimeter of the mainbody 118″. In this position, the plates can lock to the ITC by extendinginto the internal locking grooves of the outer sleeve of an ITC (such asgrooves 202 shown in FIG. 7A and 7B). The rotating inner part 117 a″ canalso be rotated to move or rotate the holding plates 119″ into aposition wherein they are not extending outside the said perimeter. Inthis position, the ITC running tool will not be latched to the ITC. Itshould be apparent for a person skilled in the art that the number ofholding plates 119″ can be chosen freely as appropriate.

The holding plates 119″ exhibit advantage over the previously mentionedholding pins 119 in that they can bear substantially larger forces.

FIG. 15 is a perspective view of parts of the running tool according tothis embodiment. In this drawing, one can see part of the holding plates119″ extending out of the main body 118″ of the holding element 117″, aswell as other previously described components.

FIG. 16 is an enlarged cross section view of parts of the running tool101″, showing the holding element 117″ from the side. In thisrepresentation, the holding plates 119″ do not extend outside theperimeter mentioned above, and are thus in an “unlatched” position. TheITC is not shown.

FIG. 17 is a cross section view showing an ITC 201′ left in the treespool after being run with a running tool as described herein, forinstance the running tool 101′ shown in FIG. 12 and FIG. 13. FIG. 18shows the same ITC 201′ with a debris cap 501′ arranged over it, forpreventing debris falling into it from above.

1-16. (canceled)
 17. A locking Locking mechanism for locking to internalor external locking grooves of a circular bore or member, the lockingmechanism comprising: respectively, characterized in that it comprises amain body comprising with a plurality of locking members arranged alongan inner or outer perimeter of the main body, the locking members beingrotatable supported on the main body about respective rotation axes; anactuation ring arranged within the inner perimeter of the main body oroutside the its outer perimeter, respectively, said actuation ringcomprising a plurality of engagement elements which extend extendinginto engagement slots of the locking members, or vice versa, so as torotate the locking members about said axes by rotation of the actuationring with respect to the main body; and wherein the locking members,according to their rotational position, are adapted to assume a lockingposition; wherein their perimeter extends a first distance radially outfrom the locking mechanism or radially inwardly from the lockingmechanism; and wherein the locking members are adapted to assume anunlocked position; and wherein said distance is shorter than the firstdistance or non-existent as the distance from the rotation axes of thelocking members to their perimeter varies along the perimeter.